In the conventional injection molding, the method is to inject a chip type metallic material in completely melting state into a mold by way of feeding from a hopper attached to the melting cylinder which is constituted standing having a tilt on the cylinder having a nozzle member at the tip portion with a heating means at an outer periphery, and an injection plunger in the inside so as to advance or retreat freely (Reference Patent 1: US 2001/0004930A1 Specification and FIG. 1 and FIG. 6).
Moreover, another method is to inject a metallic material as a semi-solid state which is prepared from a liquid metal, by a vertically equipped device wherein it is constituted by a barrel having a nozzle member at the tip portion, an axial cavity in the center and a temperature controller in the outer periphery in order to keep the lower temperature than the liquidus temperature of metal and provided in the inside of the axial cavity a screw for injection so as to rotate or slide freely, then a melting solid metallic material, such as ingot, in a hopper and feeding the liquid metal to the barrel(Reference Patent 2: U.S. Pat. No. 5,501,266 Specification and FIG. 1 and FIG. 3).
The metal molding machine in the reference patent 1 is conducted that a chip type metallic material is introduced to drop directly from a feeding opening on a liquid metal surface through a melting cylinder provided in an injection plunger. A metallic material such as zinc, magnesium or an alloy, which has such an extremely light weight, does not sink in a liquid metal immediately by own weight, however, it may become an accumulated state on the liquid metal even by equipping with an agitating means.
As getting higher, the upper portion of a chip type metallic material on a liquid metal suffers less heating from liquid metal, and melting by agitation is difficult of accomplishment to promote melting, since as in a solid state it is exposed to comparatively a longer period of time in an atmosphere of an inert gas, such as argon, the chip type material becomes just as a baked state to form easily a sludge.
A direct feeding of a chip type metallic material causes a material bridge at a falling gate of a feed opening, thereby a material feeding is difficult to accomplish a smooth falling or the material turns to solidify by an accumulation on an inner surface of a melting cylinder which is located having a tilt under the feed opening so that the accumulation becomes gradually bloated for a long run of operation which encounters a material melting obstacle or an operation obstacle of the plunger. A problem creates a need that the obstacle during operation causes a deteriorated function of the metal molding machine and has a profound effect on the quality of metallic product which is manufactured by the continuous injection molding.
As the method described in the reference patent 2, a metallic material is fed to a vertically stand barrel having an axial cavity in the center and a screw in the inside of the axial cavity as a liquid metal which is melted from a solid state material by a hopper, wherein a semi solid material, which is formed from the liquid metal by shearing/cooling while keeping a barrel below the liquidus temperature, is injected into a mold.
Moreover, since the feeding of a liquid metal is conducted until a filling of a space between the screw flights and the inside walls of the axial cavity, the difficult problem is remained unsolved by such a mold machine in which the injection is performed for a feeding method from a melting cylinder provided having a tilt under the liquid metal state.